[PATCH 7/7] drm/amdgpu: rework dma_resv handling
Christian König
ckoenig.leichtzumerken at gmail.com
Fri Jun 11 10:12:45 UTC 2021
Am 11.06.21 um 11:17 schrieb Daniel Vetter:
> On Thu, Jun 10, 2021 at 11:18:00AM +0200, Christian König wrote:
>> Drop the workaround and instead implement a better solution.
>>
>> Basically we are now chaining all submissions using a dma_fence_chain
>> container and adding them as exclusive fence to the dma_resv object.
>>
>> This way other drivers can still sync to the single exclusive fence
>> while amdgpu only sync to fences from different processes.
>>
>> Signed-off-by: Christian König <christian.koenig at amd.com>
>> ---
>> drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h | 1 +
>> drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 54 +++++++++++++----
>> drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 65 ---------------------
>> drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 3 +-
>> drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 2 +-
>> drivers/gpu/drm/amd/amdgpu/amdgpu_object.h | 1 -
>> 6 files changed, 47 insertions(+), 79 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h
>> index a130e766cbdb..c905a4cfc173 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.h
>> @@ -34,6 +34,7 @@ struct amdgpu_fpriv;
>> struct amdgpu_bo_list_entry {
>> struct ttm_validate_buffer tv;
>> struct amdgpu_bo_va *bo_va;
>> + struct dma_fence_chain *chain;
>> uint32_t priority;
>> struct page **user_pages;
>> bool user_invalidated;
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>> index 325e82621467..f6f3029f958d 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>> @@ -587,6 +587,20 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
>> goto out;
>> }
>>
>> + amdgpu_bo_list_for_each_entry(e, p->bo_list) {
>> + struct amdgpu_bo *bo = ttm_to_amdgpu_bo(e->tv.bo);
>> +
>> + e->bo_va = amdgpu_vm_bo_find(vm, bo);
>> +
>> + if (bo->tbo.base.dma_buf && !amdgpu_bo_explicit_sync(bo)) {
>> + e->chain = dma_fence_chain_alloc();
>> + if (!e->chain) {
>> + r = -ENOMEM;
>> + goto error_validate;
>> + }
>> + }
>> + }
>> +
>> amdgpu_cs_get_threshold_for_moves(p->adev, &p->bytes_moved_threshold,
>> &p->bytes_moved_vis_threshold);
>> p->bytes_moved = 0;
>> @@ -614,15 +628,6 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
>> gws = p->bo_list->gws_obj;
>> oa = p->bo_list->oa_obj;
>>
>> - amdgpu_bo_list_for_each_entry(e, p->bo_list) {
>> - struct amdgpu_bo *bo = ttm_to_amdgpu_bo(e->tv.bo);
>> -
>> - /* Make sure we use the exclusive slot for shared BOs */
>> - if (bo->prime_shared_count)
>> - e->tv.num_shared = 0;
>> - e->bo_va = amdgpu_vm_bo_find(vm, bo);
>> - }
>> -
>> if (gds) {
>> p->job->gds_base = amdgpu_bo_gpu_offset(gds) >> PAGE_SHIFT;
>> p->job->gds_size = amdgpu_bo_size(gds) >> PAGE_SHIFT;
>> @@ -644,8 +649,13 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
>> }
>>
>> error_validate:
>> - if (r)
>> + if (r) {
>> + amdgpu_bo_list_for_each_entry(e, p->bo_list) {
>> + dma_fence_chain_free(e->chain);
>> + e->chain = NULL;
>> + }
>> ttm_eu_backoff_reservation(&p->ticket, &p->validated);
>> + }
>> out:
>> return r;
>> }
>> @@ -685,9 +695,17 @@ static void amdgpu_cs_parser_fini(struct amdgpu_cs_parser *parser, int error,
>> {
>> unsigned i;
>>
>> - if (error && backoff)
>> + if (error && backoff) {
>> + struct amdgpu_bo_list_entry *e;
>> +
>> + amdgpu_bo_list_for_each_entry(e, parser->bo_list) {
>> + dma_fence_chain_free(e->chain);
>> + e->chain = NULL;
>> + }
>> +
>> ttm_eu_backoff_reservation(&parser->ticket,
>> &parser->validated);
>> + }
>>
>> for (i = 0; i < parser->num_post_deps; i++) {
>> drm_syncobj_put(parser->post_deps[i].syncobj);
>> @@ -1260,6 +1278,20 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
>>
>> amdgpu_vm_move_to_lru_tail(p->adev, &fpriv->vm);
>>
>> + amdgpu_bo_list_for_each_entry(e, p->bo_list) {
>> + struct dma_resv *resv = e->tv.bo->base.resv;
>> + struct dma_fence_chain *chain = e->chain;
>> +
>> + if (!chain)
>> + continue;
>> +
>> + dma_fence_chain_init(chain, dma_resv_excl_fence(resv),
>> + dma_fence_get(p->fence), 1);
>> +
>> + rcu_assign_pointer(resv->fence_excl, &chain->base);
> So for safety since this is now driver interface I was thinking off a
> helper which does this entire dance and _also_ adds the new fence to the
> shared slots. This way we don't let drivers open-code this rather tricky
> operation.
Well I only see this as a workaround for amdgpu and don't want to leak
it into other drivers.
If somebody else wants to adopt it we should probably consider fixing
the dma_resv object instead.
> You probably also want to then combine this with
> ttm_eu_fence_buffer_objects below I think so you're not walking this list
> 2x.
>
> Iow I'd put the fence_chain parameter into struct ttm_validate_buffer and
> then let ttm_eu_fence_buffer_objects() do this, by calling a new
> dma_resv_add_shared_excl_fence. Ideally the same helper that also Jason's
> sync_file import will use. We want to hide the inner workings of dma_resv
> as much as possible ofc.
>
> The other thing I'm wondering is whether this needs to be wrapped in a
> single seqlock or whether we don't have ordering issues if we split up the
> update here? Setting the exclusive fence before we also added it to the
> shared slot can at least violate the "shared fences signal after exclusive
> if both are present"
Uff, good point.
> Finally I guess need to sprinkle the manual garbage collector somehwere
> here too.
That is done automatically when somebody iterates the chain node.
Christian.
>
> But aside from the interface polish and correctness against races I think
> this looks solid in the big picture.
>
> Cheers, Daniel
>
>> + e->chain = NULL;
>> + }
>> +
>> ttm_eu_fence_buffer_objects(&p->ticket, &p->validated, p->fence);
>> mutex_unlock(&p->adev->notifier_lock);
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
>> index c3053b83b80c..23219fc3b28c 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
>> @@ -42,48 +42,6 @@
>> #include <linux/pci-p2pdma.h>
>> #include <linux/pm_runtime.h>
>>
>> -static int
>> -__dma_resv_make_exclusive(struct dma_resv *obj)
>> -{
>> - struct dma_fence **fences;
>> - unsigned int count;
>> - int r;
>> -
>> - if (!dma_resv_shared_list(obj)) /* no shared fences to convert */
>> - return 0;
>> -
>> - r = dma_resv_get_fences(obj, NULL, &count, &fences);
>> - if (r)
>> - return r;
>> -
>> - if (count == 0) {
>> - /* Now that was unexpected. */
>> - } else if (count == 1) {
>> - dma_resv_add_excl_fence(obj, fences[0]);
>> - dma_fence_put(fences[0]);
>> - kfree(fences);
>> - } else {
>> - struct dma_fence_array *array;
>> -
>> - array = dma_fence_array_create(count, fences,
>> - dma_fence_context_alloc(1), 0,
>> - false);
>> - if (!array)
>> - goto err_fences_put;
>> -
>> - dma_resv_add_excl_fence(obj, &array->base);
>> - dma_fence_put(&array->base);
>> - }
>> -
>> - return 0;
>> -
>> -err_fences_put:
>> - while (count--)
>> - dma_fence_put(fences[count]);
>> - kfree(fences);
>> - return -ENOMEM;
>> -}
>> -
>> /**
>> * amdgpu_dma_buf_attach - &dma_buf_ops.attach implementation
>> *
>> @@ -110,24 +68,6 @@ static int amdgpu_dma_buf_attach(struct dma_buf *dmabuf,
>> if (r < 0)
>> goto out;
>>
>> - r = amdgpu_bo_reserve(bo, false);
>> - if (unlikely(r != 0))
>> - goto out;
>> -
>> - /*
>> - * We only create shared fences for internal use, but importers
>> - * of the dmabuf rely on exclusive fences for implicitly
>> - * tracking write hazards. As any of the current fences may
>> - * correspond to a write, we need to convert all existing
>> - * fences on the reservation object into a single exclusive
>> - * fence.
>> - */
>> - r = __dma_resv_make_exclusive(bo->tbo.base.resv);
>> - if (r)
>> - goto out;
>> -
>> - bo->prime_shared_count++;
>> - amdgpu_bo_unreserve(bo);
>> return 0;
>>
>> out:
>> @@ -150,9 +90,6 @@ static void amdgpu_dma_buf_detach(struct dma_buf *dmabuf,
>> struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
>> struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
>>
>> - if (attach->dev->driver != adev->dev->driver && bo->prime_shared_count)
>> - bo->prime_shared_count--;
>> -
>> pm_runtime_mark_last_busy(adev_to_drm(adev)->dev);
>> pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
>> }
>> @@ -406,8 +343,6 @@ amdgpu_dma_buf_create_obj(struct drm_device *dev, struct dma_buf *dma_buf)
>> bo = gem_to_amdgpu_bo(gobj);
>> bo->allowed_domains = AMDGPU_GEM_DOMAIN_GTT;
>> bo->preferred_domains = AMDGPU_GEM_DOMAIN_GTT;
>> - if (dma_buf->ops != &amdgpu_dmabuf_ops)
>> - bo->prime_shared_count = 1;
>>
>> dma_resv_unlock(resv);
>> return gobj;
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>> index 1c3e3b608332..5d82120fc160 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
>> @@ -829,7 +829,8 @@ int amdgpu_gem_op_ioctl(struct drm_device *dev, void *data,
>> break;
>> }
>> case AMDGPU_GEM_OP_SET_PLACEMENT:
>> - if (robj->prime_shared_count && (args->value & AMDGPU_GEM_DOMAIN_VRAM)) {
>> + if (robj->tbo.base.import_attach &&
>> + args->value & AMDGPU_GEM_DOMAIN_VRAM) {
>> r = -EINVAL;
>> amdgpu_bo_unreserve(robj);
>> break;
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> index 96447e1d4c9c..30951b593809 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> @@ -871,7 +871,7 @@ int amdgpu_bo_pin_restricted(struct amdgpu_bo *bo, u32 domain,
>> return -EINVAL;
>>
>> /* A shared bo cannot be migrated to VRAM */
>> - if (bo->prime_shared_count || bo->tbo.base.import_attach) {
>> + if (bo->tbo.base.import_attach) {
>> if (domain & AMDGPU_GEM_DOMAIN_GTT)
>> domain = AMDGPU_GEM_DOMAIN_GTT;
>> else
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
>> index b35962702278..55d7e90eaa72 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
>> @@ -98,7 +98,6 @@ struct amdgpu_bo {
>> struct ttm_buffer_object tbo;
>> struct ttm_bo_kmap_obj kmap;
>> u64 flags;
>> - unsigned prime_shared_count;
>> /* per VM structure for page tables and with virtual addresses */
>> struct amdgpu_vm_bo_base *vm_bo;
>> /* Constant after initialization */
>> --
>> 2.25.1
>>
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